Electrolytic time delay device



Dec. 6, 1960 F. F. FARNswoRTl-l ET AL 2,962,965

ELECTROLYTIC TIME DELAY DEVICES Filed NOV. 2l, 1946 unlul 1 Y E N R 0 n A lNvENToRs EE FARNSWORTH H. E. HAR/N6 RJ.. TAYLOR fla- Dec, 6, 1960 F. F. FARNSWORTH ETAL 2,962,965

ELECTROLYTIC TIME DELAY DEVICES 2 Sheets-Sheet 2 Filed NOV. 2l, 1946 INVENTORS F.' EFR/VSWOTH H. E HAR/NG R L. TAYLOR ELECTRLYTIC T DELAY DEVICE Frank F. Farnsworth, Flanders, and Horace E. Haring and Raymond L. Taylor, Summit, NJ., assignors, by mesne assignments, to the United States of America. as represented by the Secretary of the Navy Filed Nov. 21, 1946, Ser. No. 711,302

Claims. (Cl. 1102-16) This invention relates to time delay mechanisms and particularly to time delay cells for underwater explosive devices which cells are electrolytically reactive when immersed in an electrolyte, such as sea water, to arm the explosive devices after a predetermined period of time.

In mine laying operations, the prevention of the premature arming of the mines is of the greatest importance since, obviously, a mine should remain unarmed at least long enough to permit the craft to proceed a safe distance from the mined area after it is laid. This is especially true when the fuzes used in the mines have sympathetic detonating characteristics. An object of the present invention, therefore, is the provision of a time delay mechanism for underwater use and adapted to forestall for any predetermined length of time the conditioning of underwater mines and the like for sympathetic detonation with explosions in the mined area.

Another object of the invention is to provide a time delay mechanism wherein the length of the delay is dependent upon the electrolytic destruction of one of its parts.

An additional object of the invention is to provide an electrolytic time delay arming cell of simple construction and manufacture which will aiord a high degree of reliability in its operation.

For a clear understanding of the manner in which the above and other objects and advantages of the invention may be achieved, reference may be made to the following detailed description and drawings of the invention, in which:

Fig. l is a longitudinal sectional View of a preferred embodiment of the invention, and shows how it may be used as a time-delay with an underwater electrolytic detonation device;

Fig. 2 is an end view of the device shown in Fig. l;

Fig. 3 is a longitudinal sectional view of another form of time delay mechanisms of the invention;

Fig. 4 is an end view of the device depicted in Fig. 3; and

Fig. 5 is a longitudinal sectional view of another form of electrolytic time delay cells made in accordance with the present invention.

One form of an electrolytic underwater delayed firing mechanism made in accordance with the present invention is shown in Figs. l and 2. In the device shown in Figs. l and 2, a casing 11, a bushing 12 threadably mounted thereto, and a frangible diaphragm 13 supported at its perimeter by the bushing, dene a sealed chamber 14. The diaphragm 13 may be secured to the bushing by any convenient waterproof means, as by rubber washers 16, and preferably restrained against axial movement by a nut 17 threaded into bushing 12.

Mounted on the bushing outwardly from the frangible diaphragm 13 is an electrolytic cell, shown generally at 18, composed in part of a plurality of silver chloride cathode washers 19 and a continuous magnesium anode disc 20. Disc 20 is fixed to bushing 12 by means of a llanged nut 21, and is biased outwardly by a spring 22 2,962,965 Patented Dec. 6, 1960 disposed between the disc and the bushing 12. A second chamber 23 is thus defined. The disc 20 is coated on its outer surface with a baked enamel except for a narrow annulus 25 of exposed magnesium situated opposite the circle of contact of spring 22. The washers 19 are separated from one another by spacer rings 24 and held in a unitary assembly by an eyelet 26. The washer assembly and the disc 20 are securely fastened together by means of a bolt 27 and a nut 28.

Disposed within chamber 14 is a sea battery 30 cornposed in part of alternate discs of magnesium 31 and silver-silver chloride 32 mounted on a central stud 33. The opposite electrode discs of each cell of the battery are spaced from one another by insulating washers 34, and from the stud 33 by an insulating bushing 36. Adjacent electrode discs of succeeding cells are back to back and in electrical contact. Metallic washers 37 electrically connect the opposite end electrodes of the battery to the casing 11 and stud 33, respectively. A resistance Wire 38, in series with the battery through the stud bolt 33 and the composite metal casing, is disposed in an electric detonator 39 and is adapted to fire the detonator when the sea battery 30 is immersed in salt water and thus becomes energized.

The modication depicted in Fig. 3 is somewhat different in construction and operation from that described above. In this device the electrolytic cell comprises a plurality of cathode discs of silver chloride 41 and an anode disc of magnesium 42, the component parts of the cell being held in assembled relationship by an eyelet 43. The disc 42 is coated with an insulating coating 44 of baked enamel or the like except for an annulus 46 of exposed magnesium. A second metallic eyelet 47, preferably soldered to the eyelet 43, holds the disc 42 tightly against eyelet 43 and affords electrical contact between these parts. Additional contact between the cathode discs 41 and eyelet 43 is supplied by metallic discs 48 and 49 at the extremities of the cell. insulating discs 50 and 51 prevent any possibility of direct contact of silver chloride with magnesium and consequent corrosion while the cell is in storage.

The cell 40 is securely clamped by an annular channel member 52 to a casing 53, the attachment being made along the perimeter of anode disc 42 which is insulated from the channel 52 and the casing 53 by an annular insulator 54. Perforations 56 and ports 57 provide communication between the central chamber 58 and the exterior of the casing, thereby permitting water to contact the interior as well as the exterior components of the cell when the time delay mechanism is immersed.

A plunger 59 having a ange 60 is biased in the direction of cell 40 by a coiled spring 61, and is displaced in that direction when the cell, through the electrolytic destruction of the disc 42 along annulus 46, is no longer capable of confining it.

In the modiiication depicted in Fig. 5 the magnesium anode disc 66 is insulated from the cathode silver chloride discs 67 by insulating washers 68 and from the casing 69 by an insulating sleeve 70. Disc 66 has a number of perforations 71 and is coated with an insulating coating of baked enamel or the like except for a narrow annulus 72 at which the bare magnesium metal of the disc is exposed. Casing 69 has a plurality of ports 73 which, together with perforations 71, aord communication between the interior chamber 74 and the exterior of the time-delay assembly. A plunger 76, biased in the direction of disc 66 by a spring 77, carries a resistor 78 electrically interposed between the anode disc 66 and the cathode Washers 67. Soldered connections between the spring and the casing 69 and the plunger 76, and between the plunger and the resistor 7S, assure continuity of the electrical circuit between the anode disc 66 and 3 the cathode washers 67 through the casing 69, the spring 77 and the resistor 78. Theresistor 78 is mechanically and electrically attached to the disc 66 by means of an eyelet S2 and a solder joint 83.

The proper functioning of all of the `m`o^dilications described herein is dependent upon the electrolytic destruction of the anodes of the 'electrolytic cells employed. The electrolyte employed is the salt water supplied when the time delay mechanisms are submerged in the sea in their normal use. However, any of the common electrolytes may be used to initiate the necessary electrolytic action. For an explanation ofthe manner in which the timedelays of the present invention function, .attentionis directed to Vthe modification shown in Figs. l and 2t Upon immersion in salt water, a diiererice in pt'ntential is set up' between the cathode washers 19 and the anode disc 20 resulting in the electrolytic decomposition of the disc along the annulus 2S. When this decomposition reaction has proceeded through the thickness of the disc, or substantially therethrough, the compressed spring 22 forces `the remainder of the electrolytic cell outwardly from the casing; at the same instant 4water is permitted to enter chamber 23. It is obvious that the amount of time consumed by the delay mechanism may be varied almost at will simply by selecting proper substances for anode and cathode from the large number of known materials, by increasing the thicknesses of the anode, and by otherwise altering the size and shape of the electrodes and their spacing. With the frangible diaphragm 13 -thu's exposed to the sea the detonator part of the device illustrated in Fig. 1 is armed, and will function as soon as the diaphragm 13 is ruptured by an explosion of a certain predetermined force in the vicinity. Energizati'on of "sea battery 30 immediately follows the admission 'of sea water into chamber 14 causing an electric current to dow through the resistance wire 38 imbedded in the detonating material and exploding the latter.

n Operation of the time-delay shown in Fig. 5 is much the same 'as that described above. In this device the anode disc 66 is supported by the cathode discs 67, the electrical connection between the two being the resistor 78, the plunger l76, the spring 77, and the casing 69. Soldee'd connections 'at :the points of juncture between these parts assure a good electrical connection between the principal parts of the electrolytic cell. When the timedelay mechanism is immersed in sea water, electrolytic destruction of the magnesium causes the anode disc to part at the annulus, permitting spring 77 to displace kplunger 7.6 in the direction Vof theV cell; thus, if plunger 76 functions as an larming plunger, -it may release a spring loaded firing pin for 'immediate action, vor it may expose a concussion-sensitive diaphragm for sympathetic operation with a nearby explosion. The resistor 78, being in ,series with the "external electrical connection between the anode 66 and the cathode discs 67, controls the potential difference between Vthese parts and thereby regulates the rate of decomposition of the anode due to electrolytic action. This, it is seen, is another means by Vwhich the time consumed in the delay provided `by the devices of the present invention vmay 'be regulated. The use of a resistor in series with the'electrodes of the cell is also 'advantageous because Yit reduces the effect of variation of temperature V'or salinity of the electrolyte upon the time required for electrolytic destruction of the fanode. In the time delay ymechanism shown in Fig. 3, the mechanical operation 'is similar to that just described; however, in this modification the external electrical connection between the anode 42 and the cathode discs 41 is effected through the eyelet 43.

While the present invention has been described particularly in its application to underwater ordnance, it is obvious that the principles and structure thereof are capableV of wide application and it is, therefore, not intended that the scope of the invention be limited to the applications described herein, but that it embrace any modifications and changes which fall Within 'the true spirit of the invention,` as covered by the appended claims, occurring to those skilled in the art.

What is claimed is: A Y

l. An electrolytic time delay mechanism for an underwater explosive device, comprising ananode and a cathode secured to said device in exposed and spaced apart electrically conductive relation whereby to form a shortcircuited electrolytic cell on immersion of said device in 'sea-water, a spring means movable within said device for effecting an aiming thereof, and means including at least a portion of said anode for restraining lmovement of said spring means whereby said arming will be effected only after the time delay occasioned by the lelectrolytic destruction of said portion of said anode.

2. An electrolytic time delay comprising a first electrolytic cell adapted normally to be exposed Vto sea Water, a second electrolytic cell normally sealed from sea water, and a frangible diaphragm interposed between said cells, one electrode of said first cell being adapted to seal said diaphragm from sea water and to be destroyed by electrolytic action to expose said diaphragm to sea water 3. An electrolytic time delay comprising a casing, a rst electrolytic cel-l xed by the anode Vthereof to one end of said casing and adapted normally to be exposed to sea water, a second electrolytic cell disposed within said casing and normally sealed from sea water, and a frangible diaphragm interposed between said cells, the anode of said lirst cell being of plate construction and fixed at its perimeter to seal "said casing against entry of sea water, said anode being destructible under electrolytic action to expose one side of said diaphragm to seawater.

4. An electrolytic time delay comprising a hollow casing, a irst electrolytic cell fixed to one end thereof and adapted normally to be exposed to sea water, the anode of lsaid cell forming one end of said casi-ng, detonating means fixed to the other end of said casing, a second 'electrolytic cell disposed within said casing, electrical resistance means electrically coupled to the electrodes of said second cell and disposed within said detonating means, and a frangible diaphragm interposed -between said cells and internally dividing said easing, said anode V,being destructible lby electrolytic action in sea water to expose said diaphragm to water pressure, said diaphragm being breakable under pressure to expose said second cell to sea water whereby said second cell is energized.

5. In the construction described in claim 4, an electrical insulating coating on the exterior surface of said anode and an annulus of relatively narrow Width in said coating to expose said anode to contact with sea water.

References Cited in the file of this patent FOREIGN vPATENTS 307,066 Germany June 2, 1920 

